Who is more likely to donate to a project? Someone who has donated before, or someone who hasn't?
To see if I get this right. You (op) would rather pay a donation and then have all the donation offers be removed (assuming you're signed in)? Personally I think that's a good idea too. I think if someone donates and is signed in they should have something dumb like "certified donor".
Seems like a simple change on their end. Asking for donation/showing the same ads for someone who already donates is alienating to them.
They have it every year. I donate to them regularly - they host a lot of great stuff, plus it's one of my money-making tools.